geotag

Use case

• your camera doesn't have a built-in GPS chip
• you let Google harvest your location history
• you want to add GPS EXIF metadata to the files produced by your camera

Usage

Make a backup of your photos/videos before using this code.

Before running the code:

• You need to download your Location History from Google Takeout in JSON format.

• You need to have exiftool installed on your machine an in your PATH (the script uses exiftool's JSON API to read/write EXIF to your files).

  On macOS, you can install it with brew install exiftool.

You'll probably need to update the code to get it to do exactly what you want, a way of doing that is:

• Install poetry.
• Clone this repository.
• Run poetry install, which creates a separate python environment and installs this project's dependencies inside it.
• Run poetry shell, which activates this python environment in you current shell.
• Running geotag -h should now work.
• You can modify the code, and your modified version of the code will be run when you run the geotag command

Notes

Timezones

Unfortunately, the EXIF standard only recently added a way to store the timezone in which a picture was taken (OffsetTimeOriginal field, EXIF Standard 2.31, July 2016). As a result, most cameras don't populate the field, which isn't ideal, considering we need to convert the DateTimeOriginal string to a UTC timestamp to find the closest location of the history.

If your camera doesn't populate the field, you should provide the --utc-offset-default flag (format: ±HH:MM), and its value should be equal to the the offset of your camera's time with UTC time.

Once the script has added GPS metadata to the pictures, it can use that GPS location to figure out the timezone in which each picture was taken, and update the DateTimeOriginal and OffsetTimeOriginal fields with more meaningful values.
For instance, my camera doesn't populate the timezone field, and I have configured it so that it uses UTC time. If a photo was taken in the UTC-4 timezone at 11PM, my camera saved the date as 2020.05.05 03:00AM UTC, and the script will update that value to 2020.05.04 11:00PM UTC-4. This allows me to make my photo management software show meaningful dates/times without having to think about updating my camera's clock when switching timezones or when DST starts.

ExifTool can already geotag pictures

Using the -geotag command and a KML export of the location history, ExifTool can almost do the same thing as this script. However, using a script such as this one gives me more control:

• applying some preprocessing to the location history (GPS data is noisy, and removing absurd GPS data points can make the results a lot better)
• overwriting already existing GPS data or not, using any condition
• ...

Performance

When updating the EXIF metadata of a photo, ExifTool always rewrites the whole file. Thus, adding location metadata to all your photos can make your computer rewrite 10s of gigabytes. This can take a lot of time and reduce the lifespan or your SSD / SD card.

If this is an issue for you I would recommend against adding location metadata to all your files, but only adding metadata to the files you actually end up keeping (in my case, I always add GPS metadata after exporting the files in JPEG format).

TODOs

• integration test

References

• ExifTool by Phil Harvey
• Photo geotagging using your Google location history